1 //===- FunctionResolution.cpp - Resolve declarations to implementations ---===//
3 // Loop over the functions that are in the module and look for functions that
4 // have the same name. More often than not, there will be things like:
6 // declare void %foo(...)
7 // void %foo(int, int) { ... }
9 // because of the way things are declared in C. If this is the case, patch
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Transforms/IPO.h"
15 #include "llvm/Module.h"
16 #include "llvm/SymbolTable.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Pass.h"
19 #include "llvm/iOther.h"
20 #include "llvm/Constants.h"
21 #include "llvm/Assembly/Writer.h"
22 #include "Support/Statistic.h"
26 Statistic<>NumResolved("funcresolve", "Number of varargs functions resolved");
27 Statistic<> NumGlobals("funcresolve", "Number of global variables resolved");
29 struct FunctionResolvingPass : public Pass {
32 RegisterOpt<FunctionResolvingPass> X("funcresolve", "Resolve Functions");
35 Pass *createFunctionResolvingPass() {
36 return new FunctionResolvingPass();
39 static bool ResolveFunctions(Module &M, std::vector<GlobalValue*> &Globals,
42 for (unsigned i = 0; i != Globals.size(); ++i)
43 if (Globals[i] != Concrete) {
44 Function *Old = cast<Function>(Globals[i]);
45 const FunctionType *OldMT = Old->getFunctionType();
46 const FunctionType *ConcreteMT = Concrete->getFunctionType();
48 if (OldMT->getParamTypes().size() > ConcreteMT->getParamTypes().size() &&
49 !ConcreteMT->isVarArg())
50 if (!Old->use_empty()) {
51 std::cerr << "WARNING: Linking function '" << Old->getName()
52 << "' is causing arguments to be dropped.\n";
53 std::cerr << "WARNING: Prototype: ";
54 WriteAsOperand(std::cerr, Old);
55 std::cerr << " resolved to ";
56 WriteAsOperand(std::cerr, Concrete);
60 // Check to make sure that if there are specified types, that they
63 unsigned NumArguments = std::min(OldMT->getParamTypes().size(),
64 ConcreteMT->getParamTypes().size());
66 if (!Old->use_empty() && !Concrete->use_empty())
67 for (unsigned i = 0; i < NumArguments; ++i)
68 if (OldMT->getParamTypes()[i] != ConcreteMT->getParamTypes()[i]) {
69 std::cerr << "WARNING: Function [" << Old->getName()
70 << "]: Parameter types conflict for: '" << OldMT
71 << "' and '" << ConcreteMT << "'\n";
75 // Attempt to convert all of the uses of the old function to the concrete
76 // form of the function. If there is a use of the fn that we don't
77 // understand here we punt to avoid making a bad transformation.
79 // At this point, we know that the return values are the same for our two
80 // functions and that the Old function has no varargs fns specified. In
81 // otherwords it's just <retty> (...)
83 if (!Old->use_empty()) { // Avoid making the CPR unless we really need it
84 Value *Replacement = Concrete;
85 if (Concrete->getType() != Old->getType())
86 Replacement = ConstantExpr::getCast(ConstantPointerRef::get(Concrete),
88 NumResolved += Old->use_size();
89 Old->replaceAllUsesWith(Replacement);
92 // Since there are no uses of Old anymore, remove it from the module.
93 M.getFunctionList().erase(Old);
99 static bool ResolveGlobalVariables(Module &M,
100 std::vector<GlobalValue*> &Globals,
101 GlobalVariable *Concrete) {
102 bool Changed = false;
103 assert(isa<ArrayType>(Concrete->getType()->getElementType()) &&
104 "Concrete version should be an array type!");
106 // Get the type of the things that may be resolved to us...
107 const ArrayType *CATy =cast<ArrayType>(Concrete->getType()->getElementType());
108 const Type *AETy = CATy->getElementType();
110 Constant *CCPR = ConstantPointerRef::get(Concrete);
112 for (unsigned i = 0; i != Globals.size(); ++i)
113 if (Globals[i] != Concrete) {
114 GlobalVariable *Old = cast<GlobalVariable>(Globals[i]);
115 const ArrayType *OATy = cast<ArrayType>(Old->getType()->getElementType());
116 if (OATy->getElementType() != AETy || OATy->getNumElements() != 0) {
117 std::cerr << "WARNING: Two global variables exist with the same name "
118 << "that cannot be resolved!\n";
122 Old->replaceAllUsesWith(ConstantExpr::getCast(CCPR, Old->getType()));
124 // Since there are no uses of Old anymore, remove it from the module.
125 M.getGlobalList().erase(Old);
133 static bool ProcessGlobalsWithSameName(Module &M,
134 std::vector<GlobalValue*> &Globals) {
135 assert(!Globals.empty() && "Globals list shouldn't be empty here!");
137 bool isFunction = isa<Function>(Globals[0]); // Is this group all functions?
138 GlobalValue *Concrete = 0; // The most concrete implementation to resolve to
140 assert((isFunction ^ isa<GlobalVariable>(Globals[0])) &&
141 "Should either be function or gvar!");
143 for (unsigned i = 0; i != Globals.size(); ) {
144 if (isa<Function>(Globals[i]) != isFunction) {
145 std::cerr << "WARNING: Found function and global variable with the "
146 << "same name: '" << Globals[i]->getName() << "'.\n";
147 return false; // Don't know how to handle this, bail out!
151 // For functions, we look to merge functions definitions of "int (...)"
152 // to 'int (int)' or 'int ()' or whatever else is not completely generic.
154 Function *F = cast<Function>(Globals[i]);
155 if (!F->isExternal()) {
156 if (Concrete && !Concrete->isExternal())
157 return false; // Found two different functions types. Can't choose!
159 Concrete = Globals[i];
160 } else if (Concrete) {
161 if (Concrete->isExternal()) // If we have multiple external symbols...x
162 if (F->getFunctionType()->getNumParams() >
163 cast<Function>(Concrete)->getFunctionType()->getNumParams())
164 Concrete = F; // We are more concrete than "Concrete"!
170 // For global variables, we have to merge C definitions int A[][4] with
171 // int[6][4]. A[][4] is represented as A[0][4] by the CFE.
172 GlobalVariable *GV = cast<GlobalVariable>(Globals[i]);
173 if (!isa<ArrayType>(GV->getType()->getElementType())) {
175 break; // Non array's cannot be compatible with other types.
176 } else if (Concrete == 0) {
179 // Must have different types... allow merging A[0][4] w/ A[6][4] if
180 // A[0][4] is external.
181 const ArrayType *NAT = cast<ArrayType>(GV->getType()->getElementType());
182 const ArrayType *CAT =
183 cast<ArrayType>(Concrete->getType()->getElementType());
185 if (NAT->getElementType() != CAT->getElementType()) {
186 Concrete = 0; // Non-compatible types
188 } else if (NAT->getNumElements() == 0 && GV->isExternal()) {
189 // Concrete remains the same
190 } else if (CAT->getNumElements() == 0 && Concrete->isExternal()) {
191 Concrete = GV; // Concrete becomes GV
193 Concrete = 0; // Cannot merge these types...
201 if (Globals.size() > 1) { // Found a multiply defined global...
202 // If there are no external declarations, and there is at most one
203 // externally visible instance of the global, then there is nothing to do.
205 bool HasExternal = false;
206 unsigned NumInstancesWithExternalLinkage = 0;
208 for (unsigned i = 0, e = Globals.size(); i != e; ++i) {
209 if (Globals[i]->isExternal())
211 else if (!Globals[i]->hasInternalLinkage())
212 NumInstancesWithExternalLinkage++;
215 if (!HasExternal && NumInstancesWithExternalLinkage <= 1)
216 return false; // Nothing to do? Must have multiple internal definitions.
219 // We should find exactly one concrete function definition, which is
220 // probably the implementation. Change all of the function definitions and
221 // uses to use it instead.
224 std::cerr << "WARNING: Found global types that are not compatible:\n";
225 for (unsigned i = 0; i < Globals.size(); ++i) {
226 std::cerr << "\t" << Globals[i]->getType()->getDescription() << " %"
227 << Globals[i]->getName() << "\n";
229 std::cerr << " No linkage of globals named '" << Globals[0]->getName()
235 return ResolveFunctions(M, Globals, cast<Function>(Concrete));
237 return ResolveGlobalVariables(M, Globals,
238 cast<GlobalVariable>(Concrete));
243 bool FunctionResolvingPass::run(Module &M) {
244 SymbolTable &ST = M.getSymbolTable();
246 std::map<std::string, std::vector<GlobalValue*> > Globals;
248 // Loop over the entries in the symbol table. If an entry is a func pointer,
249 // then add it to the Functions map. We do a two pass algorithm here to avoid
250 // problems with iterators getting invalidated if we did a one pass scheme.
252 for (SymbolTable::iterator I = ST.begin(), E = ST.end(); I != E; ++I)
253 if (const PointerType *PT = dyn_cast<PointerType>(I->first)) {
254 SymbolTable::VarMap &Plane = I->second;
255 for (SymbolTable::type_iterator PI = Plane.begin(), PE = Plane.end();
257 GlobalValue *GV = cast<GlobalValue>(PI->second);
258 assert(PI->first == GV->getName() &&
259 "Global name and symbol table do not agree!");
260 Globals[PI->first].push_back(GV);
264 bool Changed = false;
266 // Now we have a list of all functions with a particular name. If there is
267 // more than one entry in a list, merge the functions together.
269 for (std::map<std::string, std::vector<GlobalValue*> >::iterator
270 I = Globals.begin(), E = Globals.end(); I != E; ++I)
271 Changed |= ProcessGlobalsWithSameName(M, I->second);
273 // Now loop over all of the globals, checking to see if any are trivially
274 // dead. If so, remove them now.
276 for (Module::iterator I = M.begin(), E = M.end(); I != E; )
277 if (I->isExternal() && I->use_empty()) {
280 M.getFunctionList().erase(F);
287 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; )
288 if (I->isExternal() && I->use_empty()) {
289 GlobalVariable *GV = I;
291 M.getGlobalList().erase(GV);